This invention relates to a high pressure swivel coupling for concrete pumping systems.
Concrete placement systems have been developed employing concrete pumping apparatus for transporting the concrete from a central location to a depositing location. The concrete is trucked to the installation site and then transferred to the actual drop location through the pressurized pumping system. Each installation, of course, presents unique flow requirements. The pumping systems therefore require special design. Generally, standardized pipe sections of a rigid metal pipe and/or flexible hose are releasably connected to each other to produce a most convenient transfer flow pattern. Concrete pumping systems may employ working pressures on the order of 200 to 2,000 PSI (pounds per square inch) and under operating conditions surge pressures on the order of 8,000 and 9,000 PSI are encountered. In order to maintain an essentially liquid tight connection between the pipe sections requires relatively heavy duty pipe couplings. However, within any given system, the flow path may be changed from time to time and the interconnecting couplings should be constructed to permit convenient and rapid connection and disconnection. Various bolted and toggle-type couplings have been suggested for providing quick connection. In certain installations, the piping sections may be subjected to various twisting actions. For example, in various boom applications, interconnecting hoses are secured to the boom and move therewith. The boom may be formed with folding and relatively moving boom sections. The movement of and within the boom may exert a twisting action on the hose sections. With the rigid firm interconnection provided by conventional couplings the hose is actually twisted. Although very minor or minimal twist action will not adversly effect the hose structure, continuous twisting or heavy twisting action is particularly undesirable and may result in an eventual hose rupture. There is therefore a need for a coupling permitting a swivel or twisting movement between the adjacent hose sections thereby eliminating the twist forces applied directly on the hose. However, to provide a highly effective liquid type joint coupling which will withstand the high pumping pressures involved in concrete pumping and the like, presents difficult problems and has prevented low cost, reliable swivel couplings in concrete pumping systems.